The present invention is an outgrowth of the air pallet and air bearing patient mover development set forth in U.S. Pat. No. 3,948,344 entitled "Low Cost Air Pallet Material Handling Systems" issued Apr. 6, 1976, and U.S. Pat. No. 4,272,856 entitled "Disposable Air-Bearing Patient Mover and Valve Employed Therein" issued June 16, 1981, assigned to the common assignee. Planar air pallets of such type employ at least one flexible material bottom sheet for partially defining a plenum chamber with said one sheet being perforated as by way of small pinholes over a surface area defined by the imprint of the load which pinholes face an underlying fixed generally planar surface area, and wherein the pinholes open unrestrictedly to the interior of the plenum chamber. When the plenum chamber is pressurized by low pressure air, the escape of air under pressure through the minute perforations acts to initially jack the load above the flexible sheet and to create a frictionless air bearing of relatively small height between the underlying support surface and the bottom of the perforated flexible sheet.
In all air pallets, including patient movers, it is necessary to provide controlled pillowing of the flexible film or films which may totally or partially define the plenum chamber and to thus establish by jacking the load to a predetermined height, the ability of the air pallet to ride over surface projections on the underlying support surface. At the same time, excess pressurization of the plenum chamber may cause ballooning of the thin flexible sheet or sheets, resulting in tilting or rolling of the load off the top of the air pallet. When the load rests on the air pallet prior to pressurization of the plenum chamber, the load tends to press the perforated flexible sheet into contact with the underlying support surface (floor). This prevents the entry of air under light pressure into the plenum chamber and subsequent escape of air through the perforations to create the air bearing. Air dispersion means are required either interiorly or exteriorly of the plenum chamber or to insure pressurization of the plenum chamber, jacking of the load and subsequent creation of the air bearing.
While the air pallet type patient mover of U.S. Pat. No. 4,272,856 has operated satisfactorily, particularly in moving a patient placed thereon to and from relatively rigid underlying support surfaces, such as from an operating table to a wheeled transport table, difficulty occurs when the patient is to be moved to and from a bed whose mattress is relatively soft, and its surface is depressed so tha the deformation takes the form or contour matching the patient's body with the largest depression created by the patient's torso. It must be appreciated that a person's body is of irregular configuration in addition to the fact that the mass of the patient is also irregularly distributed. The heavy centrol torso is much heavier than the head at one end or the legs at the opposite end of that torso.
Additionally, basic to the air pallet of U.S. Pat. No. 3,948,344 is the requirement that the load constitute or be supported by a generally rigid backing member. Where such load may comprise cardboard boxes or the like, the planar bottom of such carton may constitute the generally rigid backing member or backing surface. In U.S. Pat. No. 3,948,344, where the thin flexible sheet bearing the pinhole type perforations is formed by a plastic bag or the like, the generally rigid backing member may comprise a rigid board or sheet inserted into the bag and disposed between the perforated bottom layer of the bag immediately facing the generally rigid backing member on one side and the underlying exterior and generally rigid support surface on its other side. While such rigid sheet or planar board member may operate satisfactorily under some circumstances, such an arrangement provides difficulties in air pallet type patient movers, where the patient must be moved onto or removed from a relatively soft support surface such as a hospital bed mattress having surface depressions, matching the contour of the patient and where such depressions are of irregular configuration and depth.
It is, therefore, a primary object of the present invention to provide an improved patient mover which is particularly applicable for moving the patient to and from a relatively soft and yielding support surface, such as the surface of a mattress, wherein the mass of the patient may be effectively distributed over a significant extent of the patient mover, wherein the patient mover may be readily hand grasped from either side or from either end, wherein the perforated pattern area of the thin flexible sheet facing the mattress is configured to the mass distribution of the patient carried thereby, and wherein air distribution to the plenum chamber, jacking of the patient and creation of the frictionless air film bearing are assured.